JPH1124422A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a desired image by transferring a toner image to a non plastically deformed part. SOLUTION: An intermediate transfer body 20 is arranged to come into contact with a photoreceptor 12. In a first transferring position coming into contact with the photoreceptor 12, a toner image on the photoreceptor 12 developed by a developing unit 18 is transferred to an intermediate transfer body 20. Then, the toner image on this transfer body 20 is transferred to a transfer material, in a second transferring position coming into contact with a transfer unit 24. When a mark 32 is detected by a sensor 34 after the transfer to the transfer material is completed, the rotations of the photoreceptor 12 and the transfer body 20 are stopped. In other words, during the stop of the rotation of the transfer body 20, the same part (a part to which the toner image is not transferred) of the transfer body 20 can be always brought into contact with the photoreceptor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
In particular, the present invention relates to an image forming apparatus that transfers a toner image formed on an image carrier to a transfer material via an intermediate transfer member.

[0002]

2. Description of the Related Art In a conventional image forming apparatus using an electrophotographic system, when a toner image formed on an image carrier is transferred to a transfer material such as paper, the image is transferred in accordance with the toner image on the image carrier. While transferring the material, the transfer material is charged from the back side of the transfer material, and the toner image is electrically transferred to the transfer material side. At this time, the transfer material may be held on a transfer drum (transfer unit) that rotates in synchronization with the image carrier, and the toner image may be transferred onto the transfer material held on the transfer drum.

However, when the transfer material is thick and strong, there is a problem that the transfer material cannot be held on the transfer drum, so that only a limited transfer material can be used. Therefore, after the toner image formed on the image carrier is temporarily transferred to an intermediate transfer member provided so as to be in pressure contact with the toner image, the toner image on the intermediate transfer member is transferred to a transfer material. An image forming apparatus is disclosed in Japanese Patent Publication No. Hei 4-18310 [G03G 15/16, 15:00], which was published on March 27, 1992.

[0004]

As described above, the intermediate transfer member is disposed so as to be in pressure contact with the surface of the image carrier, and the surface of the intermediate transfer member is made of an elastic material such as urethane rubber and a fluororesin. Coated. Therefore, when the image forming operation is not performed for a long period of time, that is, when a certain portion of the intermediate transfer body is left in contact with the image carrier, the portion of the intermediate transfer body that contacts the image carrier is plastically deformed. As a result, there is a problem that a uniform toner image cannot be transferred onto the intermediate transfer member.

Further, under the condition of high temperature and high humidity, there is also a problem that the organic substance in the surface layer of the intermediate transfer member bleeds, adheres to the surface of the image carrier, and the image in that portion is lost. . In order to solve these problems, a separation mechanism for separating the intermediate transfer member from the image carrier may be provided so that the intermediate transfer member is separated from the image carrier when the image forming operation is not performed. Although good, a new problem arises in that the apparatus becomes complicated and the cost increases.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an image forming apparatus which is inexpensive and can prevent image deterioration due to static contact between an image carrier and an intermediate transfer member.

[0007]

According to a first aspect of the present invention, there is provided an image bearing member for carrying a toner image developed by a developing device, and an intermediate member for transferring a toner image at a first transfer position in pressure contact with the image bearing member. In an image forming apparatus having a transfer unit that transfers a toner image transferred to a transfer body and an intermediate transfer body to a transfer material at a second transfer position, after transferring the toner image to the transfer material at the second transfer position, An image forming apparatus, wherein a predetermined portion of an intermediate transfer member is stopped at a first transfer position.

According to a second aspect of the present invention, there is provided an image carrier for carrying a toner image developed by a developing device, an intermediate transfer body on which a toner image is transferred at a first transfer position in pressure contact with the image carrier, and an intermediate transfer. An image forming apparatus including a transfer unit that transfers a toner image transferred to a body to a transfer material at a second transfer position, wherein at least one of an image carrier and an intermediate transfer body is provided with a cutout portion extending in a main scanning direction. An image forming apparatus, wherein the notch portion is stopped at a first transfer position after a toner image is transferred to a transfer material at a transfer position of No. 2.

[0009]

In the first invention, the toner image formed on the image carrier is transferred to the intermediate transfer member at a position where the image carrier and the intermediate transfer member come into contact, that is, at the first transfer position, and Is transferred to the transfer material at the transfer position of. When the predetermined portion of the intermediate transfer member after the transfer to the transfer material has reached the first transfer position, the rotation of the intermediate transfer member is stopped. That is, when the image forming operation is not being performed, a portion of the image carrier on which the toner image is not transferred is brought into contact with the image carrier.

In the second invention, when the notch provided in at least one of the intermediate transfer member and the image carrier reaches the first transfer position, the rotation of the intermediate transfer member is stopped. That is, when the image forming operation is not performed, the image carrier and the intermediate transfer member are brought into a non-contact state.

[0011]

According to the first aspect, the same portion (predetermined portion) of the intermediate transfer member is always brought into contact with the image carrier when the image forming operation is not performed. The toner image is not transferred to a portion that may be plastically deformed. Therefore, image deterioration due to static contact between the image carrier and the intermediate transfer member can be prevented at a very low cost.

According to the second aspect, when the image forming operation is not performed, the image carrier and the intermediate transfer member are brought into a non-contact state, so that the intermediate transfer member is plastically deformed or bleeds. The problem that the toner adheres to the image carrier is eliminated. The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus 10 according to this embodiment shown in FIG.
Is applied to, for example, a color laser printer in which toner images of respective colors are sequentially formed on a photoconductor 12 as an image carrier by a known electrophotographic process. In this embodiment, a drum-shaped photoconductor rotating in the direction of the arrow is used, but a belt-shaped or plate-shaped photoconductor may be used.

A charger 14 is disposed above the photoconductor 12, and the charger 14 uniformly charges the surface of the photoconductor 12. Then, the original light image (laser beam) formed by the exposure device 16 is incident on the charged photoconductor 12 via a mirror or the like (not shown), and an electrostatic latent image is formed on the photoconductor 12. On the right side of the photoreceptor 12, a plurality of color developing units 18 (four in this embodiment) are arranged. For example, black, yellow, magenta, and cyan are arranged from upstream in the rotation direction of the photoreceptor 12. You. Then, the electrostatic latent image is visualized by one of the developing units 18 according to the image information.

More specifically, image information (image data) read by an image reading device (not shown) such as an image scanner is decomposed into black, yellow, magenta, and cyan color components. It is temporarily stored in a memory (not shown). Then, the image data is read from the memory in the order of black, yellow, magenta, and cyan, and the developing device 18 corresponding to the image data of each color is activated to form a toner image on the photoconductor 12 sequentially. Therefore, when a full-color image is formed, black, yellow, magenta, and cyan toner images are formed on the photoconductor 12 every one rotation. In this manner, a single-color image is formed by rotating the photoconductor 12 once, and a color image is formed by rotating the photoconductor 12 four times.

An intermediate transfer member 20 is disposed below the photosensitive member 12 so as to be in contact therewith. As shown in FIG. 2, the intermediate transfer member 20 is formed by coating a surface of an electrode member 20a such as an aluminum tube with a semiconductive urethane rubber 20b.
The surface of Ob is coated with a fluororesin 20c. The outer diameter of the intermediate transfer body 20 is set to an integral multiple of the outer diameter of the photoconductor 12 (1 in this embodiment), and is rotated in a direction opposite to that of the photoconductor 12 by a drive motor (not shown) in synchronization with the photoconductor 12. Rotate.

By applying a predetermined bias voltage to the electrode member 20a, the toner image developed on the photoreceptor 12 by the developing device 18 is transferred to the intermediate transfer body 20 at a contact position with the intermediate transfer body 20. Transcribed. That is, at the first transfer position, the toner images formed on the photoconductor 12 are sequentially transferred to the intermediate transfer body 20.
Further, the untransferred toner on the photoconductor 12 is removed by a cleaning device 22 provided downstream of the first transfer position and upstream of the charger 14 in the rotation direction of the photoconductor 12.

Below the intermediate transfer member 20, a transfer device 24 as a transfer means is disposed, and the intermediate transfer member 20 and the transfer device 2 are arranged.
The toner image transferred to the intermediate transfer body 20 is transferred to a transfer material (not shown) conveyed along the conveyance path P at the position where the toner image contacts the intermediate transfer member 4, that is, the second transfer position. The transfer material on which the toner image has been transferred at the second transfer position is guided to the fixing device 28 by the separating means 26, where the toner image on the transfer material is fixed to the transfer material. Further, a cleaning device 30 is provided downstream of the second transfer position and upstream of the first transfer position in the rotation direction of the intermediate transfer body 20, and untransferred toner on the intermediate transfer body 20 is captured there. You.

The transfer device 24, the separating means 26, and the cleaning device 30 are provided so as to be able to freely contact and separate from the intermediate transfer member 20, and transfer the toner image on the photosensitive member 12 according to image information to the intermediate transfer member 20. Until the transfer, the transfer device 24, the separating means 26 and the cleaning device 30
Separated from A bias voltage having a polarity opposite to the polarity of the charged toner is applied to the transfer device 24.

In the above-described image forming apparatus 10 for temporarily transferring the toner image on the photosensitive member 12 to the intermediate transfer member 20 provided in contact with the photosensitive member 12, the image forming operation is not performed. If the rotation of the intermediate transfer member 20 is stopped for a long period of time, the portion of the intermediate transfer member 20 that is in contact with the photoconductor 12 is plastically deformed, and the intermediate transfer member 2
There was a problem that a uniform toner image could not be carried on the surface of the image.

On the other hand, the image forming apparatus 1 shown in FIG.
0, the mark 32 for positioning on the intermediate transfer body 20
The mark 32 is monitored by a sensor 34, and when the sensor 34 detects the mark 32,
The rotation of the intermediate transfer member 20 is stopped when the predetermined portion of the zero reaches the first transfer position. That is, when the rotation of the intermediate transfer member 20 is stopped, a portion (predetermined portion) of the photoconductor 12 where the toner image is not transferred is always in contact with the photoconductor 12. Therefore, the problem that the toner image is transferred to a portion where the plastic deformation is likely to occur and the image is deteriorated is solved.

The output of the sensor 34 is given to a CPU 36, whereby the photosensitive member 12 and the intermediate transfer member 2
The motor driver 38 for driving 0 is controlled.
That is, the CPU 36 drives the photoconductor 12 and the intermediate transfer member 20 in step S1 of FIG. 4, and applies a predetermined bias voltage to the charger 14, the developing device 18, and the intermediate transfer member 20 in step S3. I do. The CPU 36 turns on the exposure device 16 in the subsequent step S5, and turns off the exposure device 16 after a predetermined time has elapsed since the exposure device 16 was turned on. That is, the CPU 36
In step S5, exposure of image data corresponding to one page is performed.

In the next step S7, the CPU 36 determines whether or not the steps S3 and S5 have been repeated four times. That is, in step S7, the CPU 36 determines whether or not the toner images of the number of colors corresponding to the image data have been transferred to the intermediate transfer body 20. If "YES" is determined in the step S7, a predetermined bias voltage is applied to the transfer device 24 to transfer the toner image formed on the intermediate transfer body 20 to a transfer material (not shown).
When the toner image on the intermediate transfer member 20 has been transferred to the transfer material, the application of the bias voltage to the transfer device 24 is stopped,
The transfer processing at the second transfer position ends.

In step S11, the CPU 36
It is determined whether a print request has been made, and if "YES" is determined, the process returns to step S5 to repeat the above-described electrophotographic process. On the other hand, if "NO" is determined in the step S11, that is, if there is no image data of another page to be formed, in a next step S13, the charging device 14, the developing device 18 and the intermediate transfer body 20 are disabled, and , In step S15,
It is determined whether or not the sensor 34 has detected the mark 32. When the sensor 34 detects the mark 32, that is, when the predetermined portion of the intermediate transfer member 20 reaches the first transfer position, the process proceeds to step S17, and the rotation of the photosensitive member 12 and the intermediate transfer member 20 is stopped.

In this embodiment, when the intermediate transfer member 20 is not rotating, a portion (predetermined portion) of the photoconductor 12 where the toner image is not transferred is brought into contact with the photoconductor 12. In addition, the toner image is not transferred to a portion where plastic deformation is likely to occur, which does not lead to image deterioration. FIG. 5 shows an image forming apparatus 10 of another embodiment, and FIG. 7 shows an image forming apparatus 10 of another embodiment.

An image forming apparatus 10 according to another embodiment shown in FIG.
In this embodiment, a notch 40 extending in the axial center (main scanning) direction is provided on the intermediate transfer body 20, and when the notch 40 reaches the first transfer position, the rotation of the photoconductor 12 and the intermediate transfer body 20 is performed. I'm trying to stop. That is, the intermediate transfer member 20
When the rotation of the intermediate transfer member 2 is stopped,
0 is in a non-contact state. In this embodiment, the photoconductor 12 and the intermediate transfer body 20 are stopped after a predetermined time has elapsed since the sensor 34 detects the notch 40.

On the other hand, in an image forming apparatus 10 according to another embodiment shown in FIG. 7, a notch 4 similar to that of the embodiment shown in FIG.
0, and based on the output of the sensor 34, the notch 4
The photoconductor 12 and the intermediate transfer body 20 are controlled so that 0 is stopped at the first transfer position. According to these embodiments shown in FIGS. 5 and 7, when the rotation of the intermediate transfer member 20 is stopped, the photosensitive member 12 and the intermediate transfer member 20 are not in contact with each other. Can be prevented from being plastically deformed. Therefore, the problem that the organic substance in the surface layer of the intermediate transfer body 20 bleeds and adheres to the photoreceptor 12 when used under conditions of high temperature and high humidity can be solved.

In the above-described embodiment, the rotation of the intermediate transfer body 20 is controlled based on the output of the sensor 34. For example, the elapsed time from the start of the image forming operation is measured, and The rotation of the intermediate transfer body 20 may be controlled by estimating the time when the image forming operation is completed from the elapsed time. Further, it goes without saying that the present invention can be applied not only to the image forming apparatus 10 having a plurality of developing units 18 for each color as in the above-described embodiment, but also to, for example, a black and white printer.

[Brief description of the drawings]

FIG. 1 is an illustrative view showing one embodiment of the present invention;

FIG. 2 is an illustrative view showing an intermediate transfer member of the embodiment shown in FIG. 1;

FIG. 3 is a block diagram of the embodiment of FIG. 1;

FIG. 4 is a flowchart showing an example of the operation of the embodiment in FIG. 1;

FIG. 5 is an illustrative view showing another embodiment;

FIG. 6 is an illustrative view showing an intermediate transfer member of the embodiment in FIG. 5;

FIG. 7 is an illustrative view showing another embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Photoconductor 20 ... Intermediate transfer body 24 ... Transfer device 32 ... Mark 34 ... Sensor 40 ... Notch

Claims (4)

[Claims] An image bearing member for bearing a toner image developed by a developing device; an intermediate transfer member on which the toner image is transferred at a first transfer position in pressure contact with the image bearing member; and the intermediate transfer member An image forming apparatus provided with a transfer means for transferring the toner image transferred to the transfer material at a second transfer position, after transferring the toner image to the transfer material at the second transfer position, An image forming apparatus, wherein a predetermined portion of a body is stopped at the first transfer position. 2. The image forming apparatus according to claim 1, wherein the predetermined portion is a portion on which the toner image corresponding to one page formed on the image carrier is not transferred. 3. An image bearing member for bearing a toner image developed by a developing device, an intermediate transfer member on which the toner image is transferred at a first transfer position in pressure contact with the image bearing member, and the intermediate transfer member An image forming apparatus including a transfer unit that transfers the toner image transferred to the transfer material to a transfer material at a second transfer position, wherein at least one of the image carrier and the intermediate transfer member is provided with a cutout portion extending in a main scanning direction. An image forming apparatus, wherein after the toner image is transferred to the transfer material at the second transfer position, the notch is stopped at the first transfer position. 4. The image forming apparatus according to claim 3, wherein the cutout portion is formed in a portion where the toner image corresponding to one page formed on the image carrier is not transferred.